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A-Level AQA Biology > Stimuli and Response > Flashcards

Stimuli and Response Flashcards

1
Q

Where can organisms detect change?

A

External environment

Internal environment

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2
Q

Give an example of an External environment

A

Temperature of surroundings

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3
Q

Give an example of an Internal environment

A

Blood glucose concentration

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4
Q

What three components does coordinating a response to an enivorment involve?

A

Stimulus - change in the environment.

Receptors - detect the change in the environment.

Effectors - initiate the response.

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5
Q

What do effectors do in terms of reponses to an enviroment?

A

Initiate the response.

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6
Q

What do receptors do in terms of responses to an enviroment?

A

Detect the change in the environment.

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7
Q

What are Directional growth responses called?

A

Tropisms.

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8
Q

Phototropism

A

Growth in response to direct light

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9
Q

Gravitropism

A

Growth response to direction of gravity

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10
Q

What does it mean if shoots are negatively gravtropic?

A

They grow upwards (away from the gravitational pull).

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11
Q

What does it mean if shoots are postively gravitropic?

A

They grow downstairs (downwards the gravitational pull

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12
Q

Explain why shoots show positive gravitropism.

3 points

A
  1. Gravity causes IAA to accumulate on lower side of the root.
  2. IAA inhibits elongation of root cells
  3. Cells on the upper side of the root elongate faster, so the root tip bends downwards.
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13
Q

Explain why shoots show positve phototropism.

5 steps

A
  1. Indoleacetic acid (IAA) diffuses to shade side of shoot tip,
  2. As IAA diffuses down shaded side, it causes active transport of H⁺ ions into cell wall.
  3. Disruption to H-bonds between cellulose molecule & action of expansins make cell more permeable to water. (acid growth hypothesis).
  4. Cells on shaded side elongate faster due to higher turgor pressure
  5. Shoot bends towards light
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14
Q

What is Indoleacetic acid (IAA)?

A

A type of auxin that controls the tropic response in plants.

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15
Q

How can IAA be transports in short distances?

A

Through difffusion or active transport

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16
Q

How can IAA be transports in long distances?

A

In the phloem

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17
Q

What happens if the distrubution of IAA is uneven?

A

A directional growth response occurs

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18
Q

What happens If a shoot is exposed to an uneven light source?
Phototropism - roots

A

IAA is transported to the more shaded part.

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19
Q

What happens If a shoot is exposed to an uneven gravitational pull?
Gravitropism - shoots

A

IAA is transported to the underside (closer to the pull of gravity).

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20
Q

What are the two ways in which animals respond to the enviroment?

A 
Tactic reponses  (taxes)
Kinetic responses (kineses)
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21
Q

Give an example of a Tactic response

A

Woodlice move away from a light source

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22
Q

Give an example of a Kinetic response

A

Woodlice move more slowly and turn less in high humidity but move faster and turn more in low humidity.

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23
Q

Is taxes are postive or negative directioal stimulus

A

could be one or the other

24
Q

Is kineses a directional or non-directional

A

Non-directional response to presence and intensity of an external stimulus eg humidity

25
Q

How do woodlice respond to light?

A

They move away from the light

26
Q

What are choice chambers?

A

Used to study how animals respond to environmental stimuli.

27
Q

Simple Stages Involved in the Choice Chambers Experiment

A
  1. Build choice chamber
  2. Add the woodlice
  3. Collect results
  4. Repeat experiment
28
Q

Reflex arc

A

The pathway of neurones involved in a reflex response

29
Q

What are the three types of neurone involved in the relfex arc

A

Sensory
Relay
Motor

30
Q

Give an example of an reflex

A

When a person’s hand touches a very hot object, they quickly move their arm away.

31
Q

Steps in the Reflex Arc

A
  1. Detection of stimulus
  2. Sensory neuron carries impluses to the relay neuron.
  3. Relay neuron carries impluses to motor neuron
  4. Motor neuron impluses to effectors
  5. Response
32
Q

What neurone carries an impulse from thermoreceptors to a relay neurone in the spinal cord?

A

Sensory neuron

33
Q

Where does the motor neurone carry the impulse?

34
Q

Give two of the three components involved in organisms coordinating a response to changes in the environment:

A

Stimulus
Receptors
Effectors

35
Q

What name is given to growth in the response to the direction of gravity?

A

Gravitropism

36
Q

What does IAA stand for?

A

Indoleacetic acid

37
Q

What method can be used to study how animals respond to environmental stimuli?

A

Choice chambers

38
Q

Effectors

A

An organ, tissue, or cell that produces a response to a stimulus.

39
Q

The Pacinian corpuscle

A

A mechanoreceptor found in the skin

40
Q

What are plant growth factors and where are they produced?

A

Plant growth factors = Chemicals that regulate plant growth response to directional stimuli

  • Produced in plant growing regions (apical meristems).
  • Diffuse from cell to cell/phloem mass transport.
41
Q

Contrast mammalian hormones and plant growth factors. (CASTS)

Feature
Mammalian hormone
Plant growth factor

A 
Refer to PMT Flashcards
Concentration
Action
Sythesis
Transport
Speed
42
Q

Many organims respond to temperature and humidity via kinesis rather than taxis. Why?

A

Less directional stimuli; often no clear graident from one exterme to the other

43
Q

How could a student recognise kinesis in an organism’s movement?

A
  1. Organism crosses sharp division between favourable & unfavourable enviroment: turning increases (return to the original favourable enviroment.)
  2. If organism movies considerable distance into unfavourable enviroment: turning slowly decreases; begin to move in long, straight lines; sharper turns (lead to organism to new enviroment).
44
Q

Outline what happens in a simple reflex arc.

A

Receptor detects stimulus → sensory neuron → relay neuron in CNS → coordinates response → motor neuron → response by effector

45
Q

Give the advantages of a simple reflex

A
  1. Rapid response to potentially dangerous stimuli since only 3 neurons involves
  2. instinctive
46
Q

Suggest a sutiable statistical test to determine whether a factor has a significant effect on the movement of an animal in a choice chamber.

A

Chi-squared

47
Q

What features are common to all sensory receptors?

A
  • Acts as energy transducers which establish a generator potential.
  • Respond to specific stimuli
48
Q

Describe the structure of a Pacinian corpuscle.

A
  • Single nerve fibre surrounded by layers of connective tissue which are separated by viscous gel and contained by a capusle,
  • Strech-mediated Na⁺ channels on plasma membrane
  • Capillary runs along base layer of tissue
49
Q

What stimulus does a Pacinian corpuscle respond to? How?

A
  1. Pressure deforms membrane, causing stretch-mediated Na⁺ ions channels to open.
  2. If influx of Na⁺ raises membrane to theshold potential, a generator potential is produced.
  3. Action potential moves along sensory neuron.
50
Q

Name the 2 types of photoreceptor cell located in the retina.

A
  1. Cone cells.

2. Rod cells

51
Q

Where are rod and cone cells located in the retina?

A

Rod: evenly distrubted aroung periphery but NOT in central fovea

Cone: mainly central foeva no phtoreceptors at blind spot

52
Q

Compare and contrasy rod and cone cells. (PACL)

Property
Rod
Cone

A

Refer to PMT

53
Q

Outline the pathway of light from a photoreceptor to the brain.

A

Photoreceptor → bipolar neuron → ganglion cell of optic nerve → brain

54
Q

Define myogenic.

A

Contraction of heart is intiated with the muscle itself rather than by nerve impulses

55
Q

State the name and location of the 2 nodes involves in heart contraction.

A
  • Sinoatrial node (SAN): within the wall of the right atrium.
  • Atrioventricular node (AVN): near lower end of right atrium in the wall that separates the 2 atria.

A-Level AQA Biology (77 decks)

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